About 500,000 people in the United States become legally blind each year. About one-fifth of these individuals have cataracts. Although the surgical treatment of cataracts is relatively safe and effective much of the suffering and economic loss could be avoided if cataracts were prevented. Much of the problem centers around cataracts in elderly individuals. However, there are no animal models in which this type of cataract can be readily studied. Therefore, other more available models must be used with the assumptions that a detailed knowledge of the cataractogenic process of a special type can be correlated with that for other types and generalizations can be made that will have broad applications. Lens fibers constitute 90% of the lens mass and are continuously being formed from germinative cells located in the equatorial portion of the epithelium that covers the anterior surface of the lens. Cataracts in elderly individuals have been associated with the slow generation of new fibers. The development of diabetic and galactose cataracts is also associated with a failure of fiber formation. Therefore, it is the purpose of this investigation to study the process of lens fiber formation under normal and cataractogenic conditions. Tissue culture methods have been developed whereby lenses in standard media can be maintained in a transparent state without a change in lens volume for periods in excess of three weeks. In galactose media lenses can be cultured with the formation of cataracts. The lens does not grow under either one of these tissue culture situations. It is proposed, therefore, to study lens fiber formation, or growth, by seeking the reasons for differences in results under two circumstances -the growth of normal lenses in the whole animal as against no growth in tissue culture and the growth of lenses in normal animals or tissue culture against no growth under cataractogenic conditions.